# US 4,400,532 A · Cryogenically controlled direct fluorination process, apparatus and products resulting therefrom

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- Number: US 4,400,532 A
- Document ID: US4400532A
- Status: Granted
- Kind: A
- Application number: 06/284,584
- Filed: 1981-07-17
- Granted: 1983-08-23
- Earliest claimed: 1973-07-16
- Assignees: Massachusetts Institute of Technology
- Inventors: Richard J. Lagow; James L. Adcock; Norma J. Maraschin
- Web page: https://patentgrep.com/patent/US4400532A

## CPC

- C07D 265/30: not condensed with other rings
- B01J 8/02: with stationary particles, e.g. in fixed beds
- B01J 19/0013: {Controlling the temperature of the process}
- C07B 39/00: Halogenation
- C07C 17/10: of hydrogen atoms (combined with addition of halogens to unsaturated hydrocarbons C07C17/06)
- C07C 41/22: by introduction of halogens; by substitution of halogen atoms by other halogen atoms
- C07C 41/50: by reactions producing [IMAGE cpc-sch-C07C-0958.gif] groups
- C07C 43/313: containing halogen
- C07C 45/63: by introduction of halogen; by substitution of halogen atoms by other halogen atoms
- C07C 49/167: containing only fluorine as halogen
- C07C 51/04: from carboxylic acid halides
- C07C 51/363: by introduction of halogen; by substitution of halogen atoms by other halogen atoms
- C07C 51/58: Preparation of carboxylic acid halides
- C07C 291/00: Compounds containing carbon and nitrogen and having functional groups not covered by groups C07C201/00 - C07C281/00
- C07D 319/12: not condensed with other rings
- B01J 2219/00051: Controlling the temperature
- B01J 2219/00054: Controlling or regulating the heat exchange system
- B01J 2219/00058: Temperature measurement
- B01J 2219/00083: Coils
- B01J 2219/00099: the reactor being immersed in the heat exchange medium
- B01J 2219/00135: Electric resistance heaters
- B01J 2219/00155: using insulating materials or refractories
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C07B: GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR (preparation of carboxylic acid esters by telomerisation C07C67/47; telomerisation C08F)
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

An apparatus and process useful in direct fluorination of a variety of compositions, as well as the fluorinated compositions themselves, are disclosed. The apparatus comprises a cryogenic zone reactor, such as a packed column reactor, suitably divided into a plurality of independently controllable cryogenic temperature zones. Means are also provided to introduce a reactant to be fluorinated as well as to introduce a mixture of fluorine gas and an inert gas. New fluorinated compounds are also disclosed. These include: perfluoro-2-methoxyethyl ether; perfluoro-1,4-dioxane; perfluoro-2,5-diketohexane; perfluorohexamethylethane; and monohydropentadecafluoroadamantane. Additionally, new syntheses for trifluoroacetic acid, a commercially significant bulk chemical, are disclosed. One synthesis comprises producing perfluorooethyl acetate by direct fluorination using a cryogenic zone reactor, followed by hydrolysis of perfluoroethyl acetate. Two moles of the acid are produced for each mole of ester. A second synthesis comprises fluorinating an acyl chloride followed by hydrolysis of the resulting acyl fluoride.

## Claims

### Claim 1

A process for synthesizing trifluoroacetic acid comprising:
a. fluorinating ethyl acetate by a cryogenic direct fluorination procedure to produce perfluoroethyl acetate; and,
b. hydrolyzing perfluoroethyl acetate to trifluoroacetic acid.

### Claim 2 (depends on 1)

A process of claim 1 wherein said direct fluorination includes cryogenic zone control of the fluorination reaction.

### Claim 3

A direct fluorination process for producing trifluoroacetic acid, comprising:
a. providing a packed column fluorination reactor having a multiplicity of temperature zones independently controllable to a temperature within a range of about -190.degree. C. to about +20.degree. C.;
b. lowering the temperature of the first zone below the condensation point of ethyl acetate;
c. introducing ethyl acetate into said first zone while said zone is maintained at the lowered temperature whereby said ethyl acetate condenses on the column packings in said first zone;
d. introducing a source of elemental fluorine and an inert gas into said first zone, the source of elemental fluorine initially comprising a very small percentage of said mixture and which gradually rises as fluorination proceeds;
e. maintaining the temperature of said first zone until at least partial fluorination of the condensed ethyl acetate has occurred;
f. raising the temperature in said first zone to volatilize said partially fluorinated ethyl acetate and lowering the temperature in a second zone below the freezing point of said partially fluorinated ethyl acetate whereby the partially fluorinated ethyl acetate is transported to said second zone wherein it condenses on the column packings therein;
g. repeating step f until said ethyl acetate has been perfluorinated to produce perfluoroethyl acetate; and,
h. hydrolyzing said perfluoroethyl acetate to trifluoroacetic acid.

### Claim 4 (depends on 3)

A process of claim 3 wherein said source of elemental fluorine comprises fluorine gas.

### Claim 5

A cryogenic direct fluorination process comprising contacting, at a first fluorination site, a source of elemental fluorine and ethyl acetate at a temperature below the condensation point of said ethyl acetate and in the presence of a fluorination surface capable of removing heat generated during fluorination whereby said ethyl acetate is partially fluorinated, warming said first fluorination site to a temperature at which said partially fluorinated ethyl acetate volatilizes whereby it is volatilized and passes to a fresh fluorination site, lowering the temperature of said fresh fluorination site below the condensation point of said partially fluorinated ethyl acetate and contacting the partially fluorinated ethyl acetate, at said fresh site, with a source of elemental fluorine in the presence of a fluorination surface capable of removing heat generated during fluorination, repeating the warming, condensation and contacting step until said ethyl acetate is perfluorinated to produce perfluoroethyl acetate and subsequently hydrolyzing said perfluoroethyl acetate to produce trifluoroacetic acid.

### Claim 6 (depends on 5)

A process of claim 5 wherein said source of elemental fluorine comprises fluorine gas.

### Claim 7 (depends on 6)

A process of claim 6 wherein said fluorination surface capable of removing heat generated during fluorination comprises copper metal.